Pair Density Wave Instability in the Kagome Hubbard Model

Abstract: We identify a pair density wave (PDW) instability for electrons on the kagome lattice subject to onsite Hubbard $U$ and nearest neighbor $V$ interactions. Within our functional renormalization group analysis, the PDW appears with a concomitant $d$-wave superconducting (SC) instability at zero lattice momentum, where the PDW distinguishes itself through intra-unit cell modulations of the pairing function. The relative weight of PDW and $d$-wave SC is influenced by the absolute interaction strength and coupling ratio $V$/$U$. Parametrically adjacent to this domain at weak coupling, we find an intra-unit cell modulated vestigial charge density wave and an $s$-wave SC instability. Our study provides a microscopic setting for PDW in a controlled limit.